The tuning mechanic, and the energy spectrum, are used to allow the player to select certain classes of body they are interested in, and also to allow them to locate candidates in a 360 degree sphere relative to the much smaller viewport. Without it, you would have to fish around yourself blindly guessing which blurry blob might have an ELW under it, much like a five year old turns over cards in a game of memory looking for a match.
The horizontal line provided by honking is some kind of spectrum. Each class of body has a certain position in the spectrum. So icy bodies appear somewhere in the middle, asteroid clusters about a third of the way from the left and gas giants most of the way to the right. The height of the mark on the spectrum shows the total mass of the bodies in that class in the system.
Then you have the 'tuning' mechanic. You may be old enough to remember an analogue radio tuner

. If so, this should be intuitive. Having 'tuned' your scanning reticle into a particular planet class' frequency, some groups of caret marks appear above the tuner bar, and radially around the scanning reticle. These indicate where to steer the scanning reticle to (also shown as an anonymous blurry blob on the skybox). The placement and symmetry of the caret marks around your reticle indicates when you have a good aim.
Having positioned the scanning reticle correctly, you zoom in and are rewarded with a pixelated view of the distant body, and its statistics (and further information about any surface PoIs). Found bodies increase the completion percentage and are removed from the original honk spectrum.
As far as gamepad controls go, they are shown towards the bottom of the FSS screen in the video. You'll need an X and Y axis to shift the reticle, another X axis to move the tuner bar, and a zoom button.
I would also like to know this. I hope occlusion does work like this!
Not sure about the honk, but scanning bodies again will still net money if the earlier player has scanned and handed in, just no first discovery bonus.